mirror of git://gcc.gnu.org/git/gcc.git
74 lines
1.9 KiB
C
74 lines
1.9 KiB
C
/******************************************************************************
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* OpenMP Example - Matrix-vector multiplication - C/C++ Version
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* FILE: omp_matvec.c
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* DESCRIPTION:
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* This example multiplies all row i elements of matrix A with vector
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* element b(i) and stores the summed products in vector c(i). A total is
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* maintained for the entire matrix. Performed by using the OpenMP loop
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* work-sharing construct. The update of the shared global total is
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* serialized by using the OpenMP critical directive.
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* SOURCE: Blaise Barney 5/99
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* LAST REVISED:
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******************************************************************************/
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#include <omp.h>
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#include <stdio.h>
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#define SIZE 10
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int
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main ()
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{
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float A[SIZE][SIZE], b[SIZE], c[SIZE], total;
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int i, j, tid;
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/* Initializations */
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total = 0.0;
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for (i=0; i < SIZE; i++)
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{
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for (j=0; j < SIZE; j++)
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A[i][j] = (j+1) * 1.0;
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b[i] = 1.0 * (i+1);
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c[i] = 0.0;
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}
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printf("\nStarting values of matrix A and vector b:\n");
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for (i=0; i < SIZE; i++)
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{
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printf(" A[%d]= ",i);
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for (j=0; j < SIZE; j++)
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printf("%.1f ",A[i][j]);
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printf(" b[%d]= %.1f\n",i,b[i]);
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}
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printf("\nResults by thread/row:\n");
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/* Create a team of threads and scope variables */
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#pragma omp parallel shared(A,b,c,total) private(tid,i)
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{
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tid = omp_get_thread_num();
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/* Loop work-sharing construct - distribute rows of matrix */
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#pragma omp for private(j)
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for (i=0; i < SIZE; i++)
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{
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for (j=0; j < SIZE; j++)
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c[i] += (A[i][j] * b[i]);
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/* Update and display of running total must be serialized */
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#pragma omp critical
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{
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total = total + c[i];
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printf(" thread %d did row %d\t c[%d]=%.2f\t",tid,i,i,c[i]);
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printf("Running total= %.2f\n",total);
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}
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} /* end of parallel i loop */
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} /* end of parallel construct */
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printf("\nMatrix-vector total - sum of all c[] = %.2f\n\n",total);
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return 0;
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}
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